The objective of this project is to produce new information on the molecular structures and processes that underlie contraction and relaxation in cardiac and skeletal fast and slow muscle. Molecular interactions will be studied using a variety of physico-chemical techniques, and relevant segments of the proteins involved in specific interactions will be identified through sequence studies. Efforts will be made to establish correlations between physiological muscles with the hope of extending the work to such processes as cardiac hypertrophy and failure and some pathological processes in skeletal muscle.